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Lessons Learned: Corn After Corn

The 2015 growing season proved to be a challenging year. In
many areas corn and soybean yields were very good, however, current commodity
prices demand farmers evaluate the economics of all their practices including
crop rotation. In certain areas corn after corn rotations are already common.
But unless the relative commodity prices of corn and soybeans change, an
increase in corn after corn will likely occur. So what did we learn from 2015
that can be applied to the 2016 growing season when it comes to raising corn
after corn?

Nitrogen Management
One key take away from the extremely wet growing season in 2015 is the value of
nitrogen (N) management. This is crucial in corn after corn for two main
reasons. First, corn residue has a relatively high carbon to N ratio. As soil
microorganisms break the residue down in the soil, they use N that is already
present in the soil. This is why we see what is termed the “carbon penalty”.
This means it is important to apply N before or at planting to ensure there is
enough available for the continued decomposition of the corn residue along with
the growing corn plants. This early season application should ideally be
followed by a sidedress application to apply the N closer to the peak N need of
the corn crop.

The other important factor is to apply enough N to maximize
the return. Seven-year data from our central IL Practical Farm Research (PFR)®
site suggests that approximately 35 lb. of additional N is needed to maximize
profit in corn after corn versus corn after soybeans.